types of material testing deformation is the process that indicates or measures the properties or reactions of certain materials like metals, plastics, or ceramics under different conditions. The data or analysis collected from the test of materials helps determine the compatibility of CNC materials with various applications, including machinery components, tractor parts or construction machinery parts.
Most companies have a material testing laboratory with skilled experts and sophisticated equipment where they perform different tests to assess material properties and ensure a selected material meets the requirements of the intended application.
Why Is Material Testing Important In The Manufacturing?
Product engineers in different industries perform material testing for various purposes.
Gathering comprehensive data on material properties for new product development and improving existing ones, ensuring product quality.
Material testing is crucial in custom manufacturing since it helps determine the ideal material and contributes to product development, quality control, regulatory compliance, product reliability, research, and development.
It helps ensure the safety of personnel who work with such materials since some materials are extremely reactive or flammable.
Product developers and engineers test materials to assess the characteristic values of a material, identifying its areas of concern. Also, it aids the comparison of different materials to ensure the chosen materials meet product requirements.
Types Of Material Testing
Manufacturers rely on tests of materials to meet the intended application specification. These tests measure materials’ strength, toughness, ductility, reactivity, and other properties to determine their compatibility with applications. Standard material testing processes include:
Tensile Test
This material testing technology measures a material’s properties like strain, stress, and yield deformation. It subjects the material, such as metals, composites, and polymers, to a force on opposite ends and pulls it till it reaches the breaking point. A hydraulic or electric tensile testing machine is suitable for this procedure. The operator exposes the material to various forces, documents the data, and plots it to derive the stress-strain curve in a graph.
Compression Test
Compression test measures a material’s reaction under compressive loads. This mechanical testing procedure involves subjecting a material/specimen to compression or crushing loads until it fails to determine its compressive strength. Hence, the test for compression strength is critical in part production to understand the ductility, compressive strength, and modulus of elasticity. Compressive testing is ideal for testing various materials, including plastics, foams, ceramics, metals, etc.
Fatigue Testing
This fundamental mechanical testing determines a material’s reaction under fluctuating loads applied axially, flexure, or in torsion. Fatigue tests involve subjecting the material to a mean load and an alternating load. Consequently, the material will experience fatigue when it breaks.
An S-N diagram shows the data from the test. It is a plot of the number of cycles that cause failure against the amplitude of cyclical stress. Fatigue tests help predict the fatigue stress and lifespan of materials like polymers and metals.
Hardness Testing
The hardness test measures a material’s ability to resist indentation or deformation by subjecting the specimen to load until it fails/breaks. Conducting this test on the finished product is unnecessary since it is performed on the material alone. The Brinell, Rockwell, Shore, Knoop, and Vickers tests are common types of hardness tests. Besides, this test evaluates the effects of heat treatment or aging on a material’s properties.
Impact Testing
This mechanical properties testing measures the required force to break a material (its impact strength). Charpy and Izod are two tests used to determine the force to break material. Each test fractures the material to measure the energy that caused the fracture and identify the critical crack depth of the material.
The Charpy impact test determines the required force to fracture a material by dropping a pendulum at a certain height and measuring the energy from the height. Izod impact strength test can test material to a ¼ size by hitting and breaking material with a raised pivoting arm.
Torsion Testing
This test of materials measures the resistance to twisting or torsional forces, providing information on shear strength, ductility, and modulus of rigidity. It involves securing a material sample at one end and rotating it around its longitudinal axis to generate a twisting motion. The torque needed to rotate the sample is calculated, and the angle of rotation is documented.
The torsion test helps determine material properties, including shear strength, torsional strength, and torsional modulus of elasticity, especially when designing components like turbine blades, drive shafts, and gears subjected to twisting loads.
High-Speed Tensile Testing
It involves stimulating rapid loading conditions to determine the tensile properties of a raw material. High-speed tensile strength tests suit materials subjected to impact loading like automotive crash tests. It helps assess the material’s ability to withstand high strain.
Tests for Sheet Metal Forming
This measures a sheet metal’s formability and ability to withstand plastic deformation without failure. The cup drawing test, forming limit diagram (FLD), and bend test are typical sheet metal forming tests. It helps to assess a material’s compatibility with bending, drawing, and forming.
Electrical Testing
These tests assess the electrical characteristics of a material, such as dielectric strength, resistivity, and conductivity. Insulation resistance, conductivity, and dielectric strength tests are typical material electrical tests.
The conductivity test measures the materials’ ability to conduct electricity, the dielectric strength test determines the maximum electric field the material can resist before failure, and the insulation resistance test measures the materials’ resistance to insulation properties.
Thermal Testing
Thermal tests assess the material’s reaction to temperature changes, including thermal expansion, degradation, and conductivity. It is a critical test for determining the right material for thermal expansion, heat transfer, and insulation applications.
Thermal Conductivity: This test of materials measures the ability of a material to conduct heat. It is critical in deciding the ideal materials for electronic components, insulation, and heat exchangers.
Specific Heat: Engineers measure the amount of heat that causes a temperature rise in the material. It is critical in applications that require thermal storage and heat dissipation.
Thermal Expansion: It evaluates the limits to which a material can expand and contract when exposed to temperature changes. Thermal expansion tests help to design components for aerospace and construction applications where components are exposed to varying temperatures.
Destructive Vs. Non-Destructive Testing
Destructive material testing involves taking specimens from a material (metal, plastic, and composite) and testing it to its failure point to assess its reaction under extreme conditions. Since the material specimen is altered on the surface, it becomes unusable after the test. They are essential in engineering different automotive and aerospace components because material fatigue causes high-risk factors.
This test of materials is a crucial aspect of the research and production phase. Typical destructive material testing examples include flexure tests, impact tests, creep tests, compression tests, and high-speed tensile tests.
Non-destructive material testing (NDT) helps test for a material’s mechanical loading up to a specific deformation or breaking point under different environmental conditions without destroying the material permanently. This material testing technology ensures the quality of a material can withstand further processing and can handle loads reliably over the long term.
Product developers adopt this method in quality control and maintenance. Hardness tests, rebound tests, function tests, and static and dynamic friction tests are typical non-destructive material tests.
Standard Methods For Materials Testing
Companies use different methods to test materials to determine their compatibility with intended applications. Standard material testing methods include:
Dynamic Testing
In a dynamic test, the load occasionally influences the specimen over an extended period or is subjected to impact loads. A dynamic material test is a destructive test executed with quick movement (dynamic). Drop weight testers, high-speed tests (puncture or high-speed tensile tests), and pendulum impact tests are typical dynamic testing.
Static Material Testing
Loading on the specimen is slow and constant in static testing or (quasi)-static material testing. Static material testing determines the components and specimens’ deformation behavior and strength, mostly subjected to tension, flexure, shearing, compression, and torsion. This testing is performed with lower test speeds.
Cyclic Material Testing
Loading on the specimen occurs in constant recurring load cycles in the cyclic/fatigue material testing method. Depending on the machine, the load cycles can be tensile/compression, triangle shape, pulsating, or alternating load in sinusoidal shape.
Challenges In Material Testing
Manufacturers of different products encounter several setbacks when testing materials for applications. Here are some of the expected challenges when testing the reliability and performance of materials in different applications.
Inconsistent Sample Preparation
Material test results may be inaccurate due to inconsistent or faulty sample preparation. It makes comparing the outcomes across different tests complex since the sample size, geometry, and surface finish variation can influence final test outcomes. Adhere strictly to sample preparation standards and protocol to attain consistency in testing results.
Environmental Factors
Temperature, humidity, and air quality are different environmental factors affecting material test outcomes. Testing a material at temperatures other than the ones specified in the standards can affect material properties like fatigue life, ductility, and strength. It would be best to manage and note environmental conditions during material testing for accurate and repeatable results.
Budget and Time Restrictions
In some cases, the reliability of data collected during the material tests since cost and time limitations can result in fewer tests. Material tests can be costly and time-consuming, especially for complex tests or tests with extended durations, such as creep or fatigue testing. Therefore, you need to carefully plan and prioritize the need for comprehensive testing, cost, and time. Hence, accelerated testing methods should be employed when necessary.
Safety Issues
It can be quite difficult to ensure safety during material testing without compromising the accuracy of the conducted test. Some material testing types, particularly those involving corrosive environments, high temperatures, or loads, can pose safety risks to personnel. However, it would help to implement strict safety protocols and use safety gear to mitigate risks during test procedures.
Testing Equipment Error
It is possible to collect erroneous data due to inaccurate or poorly maintained material testing equipment. Calibration errors often result in inaccurate measurements when determining the actual material properties, which consequently causes material failure in application. Therefore, calibrate and maintain testing equipment according to manufacturer’s guidelines and industry standards to ensure accuracy.
Material Variability
There may be inconsistent test results due to the material’s inherent variability. Variations in a material’s microstructure, composition, and processing history make test outcomes different. As a result, experts advise testing multiple samples from different batches and understanding the natural variability to ensure accurate characterization.
What Industries Are Materials Testing Used?
Several products undergo thorough material testing to derive comprehensive data on their properties to ensure end products’ safety, performance, and reliability. Typical industry applications of material testing include:
Automotive
Automotive manufacturers use different carefully tested materials to produce car prototyping and components, including body frames, interior components, tires, and engine components. These tests assess these materials’ durability, fatigue resistance, and crashworthiness to ensure they are compatible.
Medical
Materials used for medical device prototypes and equipment like prosthetics, implants, and surgical instruments are tested for biocompatibility, durability, and strength to ensure the product’s effectiveness and patient’s safety.
Building and Construction
Engineers test materials like steel, composites, and asphalt used in building and construction to ensure they can withstand consistent stresses and extreme conditions and comply with safety standards.
Conclusion
Material testing is critical in every design and manufacturing field to understand the selected material’s properties and predict the manufacturing outcome. There are different tests and methods for evaluating the properties of a material to ensure reliability and quality assurance in finished products.
